As is well known in the art, in order for a golf ball to travel a distance when launched, the rebound properties of the ball itself and the sophisticated arrangement of dimples on the ball surface to reduce the air resistance of the ball in flight are important. To reduce the air resistance, many methods of uniformly arranging dimples over the entire ball surface at a higher density have been proposed.
Most often, dimples are indentations of circular shape as viewed in plane. To arrange such circular dimples at a high density, it will be effective to reduce the width of a land partitioning two adjoining dimples to nearly zero. However, the region surrounded by three or four circular dimples becomes a land of generally triangular or quadrangular shape having a certain area, as part of the spherical surface. On the other hand, it is requisite to arrange dimples on the spherical surface as uniformly as possible. Thus the arrangement density of circular dimples must find a compromise.
Under the circumstances, Kasashima et al., U.S. Pat. No. 6,595,876 (JP-A 2001-212260) attains the purpose of uniformly arranging dimples on a golf ball at a high density, by arranging dimples of 2 to 5 types having different diameters on the spherical surface of the ball which is assumed to be a regular octahedron or icosahedron.
However, as long as circular dimples are used, the percent occupation of the total area of lands (as parts of the spherical surface) over the entire golf ball surface area encounters a practical lower limit of approximately 25%. In order to further reduce the air resistance of a ball in flight, it would be desirable if the dimples arranged on the ball surface are devised so as to reduce the percent occupation of the total land area over the entire golf ball surface area.